If you previously set up Flipper AND the Channel Buttons were working, but STOPPED working:
Check the batteries. We have seen batteries such as "Energizer Max," "Lithium Ultimate" Duracell "Power Boost" (and other similar boost type) create a static charge on the board.
Solution: Take out the batteries, let the charge dissipate. Then replace the batteries with normal non Max or Boost type batteries, Flipper should work going forward. No need to reprogram.
Thank you for your understanding.